It is the scarring from the radiation that causes the swallowing difficulties. What is most important is for your husband to do his swallowing exercises religiously every day. It happened to my husband and the oncologist said he was surprised by how much scarring there was taking place. It is internal. Doing the exercises makes it less likely he will suffer from atrophy of the swallowing muscles. My husband was fed with a feeding tube. Eventually we found an interventional radiologist who used magnets to open up his esophagus which was totally closed. But then he developed silent aspiration and that led to pneumonia. Do find out if you can access the services of a speech and language pathologist at your hospital. She can do a swallowing test and show you how the liquids go down into the esophagus. She will also be able to give your husband more exercises that can help with his swallowing. She can recommend the types of food your husband should be eating and the thickness (e.g. honey grade, nectar grade and spoon grade). It’s important, please get help ASAP.